In order to assist understanding of a foreign language, there has been conventionally developed a technique of displaying a translation result of a foreign language included in an image captured by a camera in a state in which the translation result is superimposed on the image. Such a technique typically uses optical character recognition (hereinafter, referred to as “OCR”) for extraction of a character string included in an image. Though extraction of a character string is typically performed on a per-line basis in OCR, translation of the character string should be performed on a per-sentence basis for improving translation accuracy. Under the circumstances, there has been known a technique of determining an end of a sentence of a character string extracted on the per-line basis. For example, Patent Literature 1 discloses a technique of determining an end of a sentence on the basis of a period. According to the technique disclosed in Patent Literature 1, in a case where a character string is composed only of alphanumeric characters or nouns, the character string will be determined to be a single sentence even if it does not have a period.